Since environmental regulations are becoming stricter in recent years, hydrocracking catalysts are in extensive use as functional materials for producing high-quality clean fuels in the petroleum refining industry. Meanwhile, the crude oil which are being excavated are shifting to heavier oil, and the performances required of petroleum refining catalysts including hydrocracking catalysts are becoming higher year by year. In general, many of the kerosene and gas oil fractions obtained from heavy crude oil have a high aromatic hydrocarbon compound content and a high nitrogen content. It is known that these components accelerate coke deposition on the catalysts and cause deactivation of the hydrocracking catalysts.
As a result of a decrease in the demand for heavy oil and the like, the throughput in fluid catalytic cracking unit (FCC unit) and cokers has increased and the amount of the LCO (cycle oil from catalytic cracking unit) and coker cracking gas oil yielded in these units are increasing accordingly. There is a growing desire for conversion of these fractions into a useful gasoline basestock, petrochemical feedstocks, and the like through hydrocracking.
Under such circumstances, many investigations on zeolites, which are active ingredients for cracking of hydrocarbon oil, are recently being made with respect to improvements in the properties and compositions of zeolites, addition of a metal or other substance to zeolites, etc. Results of the development of novel hydrocracking catalysts have been reported.
For example, patent document 1 discloses a catalyst obtained by supporting metal having hydrotreating activity on zeolite support obtained by incorporating titania into zeolite and preparing so as to have a specific aluminum/silicon atomic ratio.
Patent document 2 discloses a catalyst obtained by supporting a metal having hydrotreating activity on zeolite support which has a specific aluminum/silicon atomic ratio and to which mesopores having a pore diameter of 50-1,000 Å have been imparted. Furthermore, patent document 3 discloses a catalyst including zeolite support which has a specific lattice constant and a specific aluminum/silicon atomic ratio and into which a metallic element in Group 4 of the periodic table has been incorporated.